| From: | Andres Freund <andres(at)anarazel(dot)de> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com>, Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>, Robert Haas <robertmhaas(at)gmail(dot)com>, David Rowley <david(dot)rowley(at)2ndquadrant(dot)com>, Amit Langote <amitlangote09(at)gmail(dot)com>, Amit Langote <Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp>, Jesper Pedersen <jesper(dot)pedersen(at)redhat(dot)com>, Rajkumar Raghuwanshi <rajkumar(dot)raghuwanshi(at)enterprisedb(dot)com>, Beena Emerson <memissemerson(at)gmail(dot)com>, amul sul <sulamul(at)gmail(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>, Dilip Kumar <dilipbalaut(at)gmail(dot)com> |
| Subject: | Re: [HACKERS] Runtime Partition Pruning |
| Date: | 2019-05-24 16:24:28 |
| Message-ID: | 20190524162428.ipyotroegpaeqebi@alap3.anarazel.de |
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| Lists: | pgsql-hackers |
Hi,
On 2019-05-24 12:08:57 -0400, Tom Lane wrote:
> Andres Freund <andres(at)anarazel(dot)de> writes:
> > On 2019-05-24 11:34:58 -0400, Tom Lane wrote:
> >> Hmm, after some digging in the archives, the closest thing I can find
> >> is this thread:
> >> https://www.postgresql.org/message-id/flat/CAMsr%2BYGL%2ByfWE%3DJvbUbnpWtrRZNey7hJ07%2BzT4bYJdVp4Szdrg%40mail.gmail.com
> >> where we discussed using libunwind instead, but people didn't like
> >> the extra dependency.
>
> > Hm, I didn't actually see that much concern about that. I still think we
> > should just go for libunwind.
>
> Is it actually better?
I've not looked in a while, but I think at some point it was.
> The basic problem with backtrace() is that it
> only knows about global functions, and so reports call sites in static
> functions as if they were in whatever global function physically precedes
> the static one.
Does that depend on whether the program was compiled with
-fno-omit-frame-pointer? At least some distros now compile with frame
pointers enabled, to get reasonably fast perf profiles (at a basically
immeasurable slowdown, on modern-ish CPUs).
> I think doing materially better requires depending on
> debug symbols, which (at least in the Red Hat world) aren't going to
> be there in a typical production situation.
It's still a lot easier to install debug symbols than to attach a
debugger and get a backtrace that way. Especially when the problem is
hard to reproduce.
Greetings,
Andres Freund
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